<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.6.14/dist/vue.js"></script>
</head>

<body>
    <div id="app">
        <p><input type="text" v-model="msg" @keyup.enter="handleEnter"></p>
        {{msg}}
        <p v-for="item of arr" @click="handleDelete(item)">{{item}}</p>
    </div>
    <script>
        new Vue({
            data() {
                return {
                    msg: "",
                    arr: []
                }
            },
            methods: {
                handleEnter() {
                    if (this.arr.indexOf(this.msg) == -1) {
                        this.arr.push(this.msg)
                    } else {
                        alert("数据已经存在")
                    }
                },
                handleDelete(val) {
                    var index = this.arr.findIndex(item => item == val)
                    this.arr.splice(index, 1)
                }
            },
        }).$mount("#app")
    </script>
</body>

</html>